1. Field of the Invention
The present invention relates in general to seat slide devices for use in motor vehicles or the like, and more particularly to seat slide devices of a type having a position adjuster by which a fore-and-aft position of the associated seat can be adjusted. More specifically, the present invention are concerned with seat slide devices of a type which is constructed to be mounted on a stepped floor.
2. Description of the Prior Art
In order to clarify the task of the present invention, one conventional seat slide device 100 of the above-mentioned type will be described with reference to FIGS. 5 and 6 of the accompanying drawings.
The device 100 comprises a pair of parallel rail units 1a and 1b which are tightly mounted on a stepped floor 200 of a motor vehicle. That is, one rail unit 1a is mounted to a higher mounting portion 200a of the floor 200, while the other rail unit 1b is mounted through supporting brackets 4 to a lower mounting portion 200b of the floor 200. Due to usage of the supporting brackets 4, the two rail units 1a and 1b are kept leveled with each other.
Each rail unit 1a or 1b comprises a stationary lower rail 3 which is connected in a stationary manner movable to the floor 200, and a upper rail 2 which is slidably engaged with the lower rail 3 and which has mounted thereon on a seat 300 (see FIG. 6).
Each rail unit 1a or 1b also has a lock device 5 by which the upper rail 2 can be locked to the lower rail 3 at a desired fore-and-aft position. The lock device 5 comprises a locking member 5a which is pivotally held by the upper rail 2 and lockingly engageable with notches formed in the lower rail 3.
The locking members 5a of these two lock devices 5 are secured to respective ends of a generally U-shaped control lever 6 which protrudes forward. Although not shown in the drawings, a spring is associated with each locking member 5a to bias the same in a direction to achieve a locked engagement with the notches of the lower rail 3. Usually, that is, when the control lever 6 is kept released, each locking member 5a is in locked engagement with the notches of the lower rail 3 causing the seat 300 to be locked at a desired fore-and-aft position. However, when the control lever 6 is pulled against the biasing force of the springs, each locking member 5a is disengaged from the notches of the lower rail 3. Thus, when the control lever 6 is kept pulled against the biasing force, the seat 300 is permitted to move forward or rearward to a new fore-and-aft position. The seat slide device of this type is disclosed in U.S. Pat. No. 4,949,932 granted Aug. 21, 1990 to Masanori Terai.
However, due to its inherent construction, the above-mentioned conventional seat slide device 100 hay,the following drawbacks.
That is, the provision of the supporting brackets 4a and 4b for raising the position of the rail unit 1b tends to cause an unstable arrangement of the seat slide device 100 with respect to the stepped floor 200. In fact, due to usage of the supporting brackets 4a and 4b, the stability of the rail unit 1b is poor in comparison with the other rail unit 1a which is intimately or stably secured to the floor 200. Furthermore, usage of the brackets 4a and 4b which are large in size, increases the weight of the vehicle on which the seat slide device 100 is mounted.